scholarly journals Glacier-surge mechanisms promoted by a hydro-thermodynamic feedback to summer melt

2015 ◽  
Vol 9 (1) ◽  
pp. 197-215 ◽  
Author(s):  
T. Dunse ◽  
T. Schellenberger ◽  
J. O. Hagen ◽  
A. Kääb ◽  
T. V. Schuler ◽  
...  
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheets ◽  
Glacier Mass Balance ◽  
Internal Dynamic ◽  
Svalbard Archipelago ◽  
Flow Acceleration ◽  
Ice Cap ◽  
Surface Melt

Abstract. Mass loss from glaciers and ice sheets currently accounts for two-thirds of the observed global sea-level rise and has accelerated since the 1990s, coincident with strong atmospheric warming in the polar regions. Here we present continuous GPS measurements and satellite synthetic-aperture-radar-based velocity maps from Basin-3, the largest drainage basin of the Austfonna ice cap, Svalbard. Our observations demonstrate strong links between surface-melt and multiannual ice-flow acceleration. We identify a hydro-thermodynamic feedback that successively mobilizes stagnant ice regions, initially frozen to their bed, thereby facilitating fast basal motion over an expanding area. By autumn 2012, successive destabilization of the marine terminus escalated in a surge of Basin-3. The resulting iceberg discharge of 4.2±1.6 Gt a−1 over the period April 2012 to May 2013 triples the calving loss from the entire ice cap. With the seawater displacement by the terminus advance accounted for, the related sea-level rise contribution amounts to 7.2±2.6 Gt a−1. This rate matches the annual ice-mass loss from the entire Svalbard archipelago over the period 2003–2008, highlighting the importance of dynamic mass loss for glacier mass balance and sea-level rise. The active role of surface melt, i.e. external forcing, contrasts with previous views of glacier surges as purely internal dynamic instabilities. Given sustained climatic warming and rising significance of surface melt, we propose a potential impact of the hydro-thermodynamic feedback on the future stability of ice-sheet regions, namely at the presence of a cold-based marginal ice plug that restricts fast drainage of inland ice. The possibility of large-scale dynamic instabilities such as the partial disintegration of ice sheets is acknowledged but not quantified in global projections of sea-level rise.

scholarly journals Destabilisation of an Arctic ice cap triggered by a hydro-thermodynamic feedback to summer-melt

2014 ◽  
Vol 8 (3) ◽  
pp. 2685-2719 ◽  
Author(s):  
T. Dunse ◽  
T. Schellenberger ◽  
A. Kääb ◽  
J. O. Hagen ◽  
T. V. Schuler ◽  
...  
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
Drainage Basin ◽  
Ice Sheets ◽  
Polar Regions ◽  
Svalbard Archipelago ◽  
Flow Acceleration ◽  
Ice Cap ◽  
Global Sea Level

Abstract. Mass loss from glaciers and ice sheets currently accounts for two-thirds of the observed global sea-level rise and has accelerated since the 1990s, coincident with strong atmospheric warming in the Polar Regions. Here we present continuous GPS measurements and satellite synthetic aperture radar based velocity maps from the Austfonna ice cap, Svalbard, that demonstrate strong links between surface-melt and multiannual ice-flow acceleration. We identify a hydro-thermodynamic feedback that successively mobilizes stagnant ice regions, initially frozen to their bed, thereby facilitating fast basal motion over an expanding area. By autumn 2012, successive destabilization of the marine terminus escalated in a surge of the ice cap's largest drainage basin, Basin-3. The resulting iceberg discharge of 4.2 ± 1.6 Gt a−1 over the period April 2012 to May 2013 triples the calving loss from the entire ice cap. After accounting for the terminus advance, the related sea-level rise contribution of 7.2 ± 2.6 Gt a−1 matches the recent annual ice-mass loss from the entire Svalbard archipelago. Our study highlights the importance of dynamic glacier wastage and illuminates mechanisms that may trigger a sustained increase in dynamic glacier wastage or the disintegration of ice-sheets in response to climate warming, which is acknowledged but not quantified in global projections of sea-level rise.

scholarly journals Multi-year surface velocities and sea-level rise contribution of the Basin-3 and Basin-2 surges, Austfonna, Svalbard

2017 ◽  
Author(s):  
Thomas Schellenberger ◽  
Thorben Dunse ◽  
Andreas Kääb ◽  
Thomas Vikhamar Schuler ◽  
Jon Ove Hagen ◽  
...  
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
Maximum Velocity ◽  
Surface Velocity ◽  
Published Data ◽  
Ice Cap ◽  
Total Mass Loss ◽  
Speed Up ◽  
Frontal Ablation

Abstract. Basin-3, the largest outlet basin of the Austfonna ice cap, started to surge in autumn 2012. A maximum velocity of 18.8 m d-1 was found in December 2012 / January 2013. Here we present a time series of area wide velocity fields from synthetic aperture radar (SAR) offset tracking and Global Positioning System (GPS) data in the aftermath of the velocity maximum, extending the previously published data from May 2013 to July 2016. We find that terminus velocity slowed down by ~ 50 % until spring 2014, whereas the upper parts of the basin continued to speed-up and reached their maximum only in summer 2014. Until the date of writing (July 2016), Basin-3 maintained high velocity with maxima between 8.9–11.4 m d-1. Summer speed-ups were superimposed even on the otherwise fast surge motion. The total frontal ablation Af over the period 19 April 2012 to 26 July 2016 was calculated to 22.2 ± 8.1 Gt (5.2 ± 1.9 Gt yr-1) from the ice mass flux qfg = 33.2 ± 11.5 Gt (7.8 ± 2.7 Gt yr-1) and the terminus mass change qt = 11.0 ± 3.4 Gt (2.6 ± 0.8 Gt yr-1). Additional advance of the terminus led to a total sea-level rise equivalent of 31.3 ± 11.2 Gt (7.3 ± 2.6 Gt yr-1). This rate of frontal ablation roughly equals previous estimates of both the calving flux and total mass loss from the entire archipelago, resulting in a doubling of the current ice-mass loss from Svalbard. In vicinity of Basin-3, we also observe a terminus advance and a speed-up of the northern part of Basin-2 starting in autumn 2014, with surface velocity reaching 8.71 m d-1 in August 2015. The related ice mass loss of Basin-2 between 20 June 2015 and 26 July 2016 amounts to 0.8 Gt (min: 0.3 Gt, max: 1.6 Gt). Accounting also for the replacement of ocean water, we find a total sea-level rise equivalent of 1.1 Gt (min: 0.5 Gt, max: 2.1 Gt).

scholarly journals Accelerated contributions of Canada's Baffin and Bylot Island glaciers to sea level rise over the past half century

2012 ◽  
Vol 6 (5) ◽  
pp. 1103-1125 ◽  
Author(s):  
A. Gardner ◽  
G. Moholdt ◽  
A. Arendt ◽  
B. Wouters
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
Integrated Approach ◽  
Mass Change ◽  
Total Contribution ◽  
Ice Cap ◽  
Past Half Century ◽  
Digital Elevation ◽  
Grace Satellite Gravimetry

Abstract. Canadian Arctic glaciers have recently contributed large volumes of meltwater to the world's oceans. To place recently observed glacier wastage into a historical perspective and to determine the region's longer-term (~50 years) contribution to sea level, we estimate mass and volume changes for the glaciers of Baffin and Bylot Islands using digital elevation models generated from airborne and satellite stereoscopic imagery and elevation postings from repeat airborne and satellite laser altimetry. In addition, we update existing glacier mass change records from GRACE satellite gravimetry to cover the period from 2003 to 2011. Using this integrated approach, we find that the rate of mass loss from the region's glaciers increased from 11.1 ± 3.4 Gt a−1 (271 ± 84 kg m−2 a−1) for the period 1963–2006 to 23.8 ± 6.1 Gt a−1 (581 ± 149 kg m−2 a−1) for the period 2003–2011. The doubling of the rate of mass loss is attributed to higher temperatures in summer with little change in annual precipitation. Through both direct and indirect effects, changes in summer temperatures accounted for 70–98% of the variance in the rate of mass loss, to which the Barnes Ice Cap was found to be 1.7 times more sensitive than either the Penny Ice Cap or the region's glaciers as a whole. This heightened sensitivity is the result of a glacier hypsometry that is skewed to lower elevations, which are shown to have a higher mass change sensitive to temperature compared to glacier surfaces at higher elevations. Between 2003 and 2011 the glaciers of Baffin and Bylot Islands contributed 0.07 ± 0.02 mm a−1 to sea level rise accounting for 16% of the total contribution from glaciers outside of Greenland and Antarctica, a rate much higher than the longer-term average of 0.03 ± 0.01 mm a−1 (1963 to 2006).

scholarly journals Long-term contributions of Baffin and Bylot Island Glaciers to sea level rise: an integrated approach using airborne and satellite laser altimetry, stereoscopic imagery and satellite gravimetry

2012 ◽  
Vol 6 (2) ◽  
pp. 1563-1610 ◽  
Author(s):  
A. S. Gardner ◽  
G. Moholdt ◽  
A. Arendt ◽  
B. Wouters
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
Integrated Approach ◽  
Laser Altimetry ◽  
Satellite Gravimetry ◽  
Ice Cap ◽  
Digital Elevation ◽  
Grace Satellite Gravimetry ◽  
Summer Temperatures

Abstract. Canadian Arctic glaciers have recently contributed large volumes of meltwater to the world's oceans. To place recently observed glacier wastage into a historical perspective and to determine the region's longer-term (~50 years) contribution to sea level, we estimate mass and volume changes for the glaciers of Baffin and Bylot Islands using Digital Elevation Models generated from airborne and satellite stereoscopic imagery and elevation postings from repeat airborne and satellite laser altimetry. In addition, we update existing glacier mass change records from GRACE satellite gravimetry to cover the period from 2003 to 2011. Using an integrated approach we find that the rate of mass loss from the region's glaciers increased from 11.1 ± 1.8 Gt a−1 (–270 ± 40 kg m−2 a−1) in 1963–2006 to 23.8 ± 3.1 Gt a−1 (–580 ± 80 kg m2 a−1) in 2003–2011. The doubling of the rate of mass loss is attributed to higher temperatures in summer with little change in annual precipitation. Through both direct and indirect effects, changes in summer temperatures accounted for 68–98 % of the variance in the rate of mass loss to which the Barnes Ice Cap was found to be 1.6 times more sensitive than either the Penny Ice Cap or the regions glaciers as a whole. Between 2003 and 2011 the glaciers of Baffin and Bylot Islands contributed 0.07 ± 0.01 mm a−1 to sea level rise, a rate equivalent to the contribution coming from Patagonian glaciers. Over the 48-year period between 1963 and 2011 the glaciers of Baffin and Bylot Islands contributed 1.7 mm to the world's oceans.

Relative control of bedrock roughness versus topography on global glacier bed friction

2021 ◽  
Author(s):  
Olivier Gagliardini ◽  
Fabien Gillet-Chaulet ◽  
Florent Gimbert
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Inverse Method ◽  
Ad Hoc ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Grid Resolution ◽  
Classical Approach ◽  
Bed Topography ◽  
Bed Friction

<p>Friction at the base of ice-sheets has been shown to be one of the largest uncertainty of model projections for the contribution of ice-sheet to future sea level rise. On hard beds, most of the apparent friction is the result of ice flowing over the bumps that have a size smaller than described by the grid resolution of ice-sheet models. To account for this friction, the classical approach is to replace this under resolved roughness by an ad-hoc friction law. In an imaginary world of unlimited computing resource and highly resolved bedrock DEM, one should solve for all bed roughnesses assuming pure sliding at the bedrock-ice interface. If such solutions are not affordable at the scale of an ice-sheet or even at the scale of a glacier, the effect of small bumps can be inferred using synthetical periodic geometry. In this presentation,<span>  </span>beds are constructed using the superposition of up to five bed geometries made of sinusoidal bumps of decreasing wavelength and amplitudes. The contribution to the total friction of all five beds is evaluated by inverse methods using the most resolved solution as observation. It is shown that small features of few meters can contribute up to almost half of the total friction, depending on the wavelengths and amplitudes distribution. This work also confirms that the basal friction inferred using inverse method<span>  </span>is very sensitive to how the bed topography is described by the model grid, and therefore depends on the size of the model grid itself.<span> </span></p>

scholarly journals Decadal-scale onset and termination of Antarctic ice-mass loss during the last deglaciation

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Michael E. Weber ◽  
Nicholas R. Golledge ◽  
Chris J. Fogwill ◽  
Chris S. M. Turney ◽  
Zoë A. Thomas
Keyword(s):  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
Ross Sea ◽  
Ice Sheet ◽  
Rate Of Change ◽  
Last Deglaciation ◽  
Decadal Scale ◽  
Ice Sheet Modeling ◽  
Global Sea Level

AbstractEmerging ice-sheet modeling suggests once initiated, retreat of the Antarctic Ice Sheet (AIS) can continue for centuries. Unfortunately, the short observational record cannot resolve the tipping points, rate of change, and timescale of responses. Iceberg-rafted debris data from Iceberg Alley identify eight retreat phases after the Last Glacial Maximum that each destabilized the AIS within a decade, contributing to global sea-level rise for centuries to a millennium, which subsequently re-stabilized equally rapidly. This dynamic response of the AIS is supported by (i) a West Antarctic blue ice record of ice-elevation drawdown >600 m during three such retreat events related to globally recognized deglacial meltwater pulses, (ii) step-wise retreat up to 400 km across the Ross Sea shelf, (iii) independent ice sheet modeling, and (iv) tipping point analysis. Our findings are consistent with a growing body of evidence suggesting the recent acceleration of AIS mass loss may mark the beginning of a prolonged period of ice sheet retreat and substantial global sea level rise.

GlacierMIP3 global glacier mass change equilibration experiments - rationale and experimental design

2021 ◽  
Author(s):  
Harry Zekollari ◽  
Regine Hock ◽  
Ben Marzeion ◽  
Fabien Maussion ◽  
Lilian Schuster ◽  
...  
Keyword(s):  
Experimental Design ◽  
Sea Level ◽  
Ice Sheets ◽  
Global Scale ◽  
Mass Change ◽  
Glacier Mass Balance ◽  
Model Intercomparison ◽  
Climate Conditions ◽  
Equilibrium Volume ◽  
Global Mean

<p>Glaciers outside the ice sheets are major contributors to today’s sea-level rise and are projected to remain so in the coming century. With the goal to better assess the future sea-level contribution from glaciers and to quantify related uncertainties, the Glacier Model Intercomparison Project (GlacierMIP) has set out to develop a series of coordinated experiments to be run as a community-wide effort.</p><p>The first two phases of the GlacierMIP have focused on the evolution of glaciers throughout the 21<sup>st</sup> century (Hock et al., 2019; Marzeion et al., 2020). In the third phase of GlacierMIP (GlacierMIP3 – equilibration), a new set of experiments has been designed to investigate the equilibration of glaciers under constant climate conditions. These experiments will allow us to answer the following fundamental questions:</p><p>1. What would be the equilibrium volume and area of all glaciers outside the ice sheets if global mean temperatures were to stabilize at present-day levels?</p><p>2. What would be the equilibrium volume and area of all glaciers outside the ice sheets if global mean temperatures were to stabilize at different temperature levels (e.g. +1.5, +2, relative to pre-industrial)?</p><p>3. For each of these global mean temperature stabilization scenarios, how much time would the glaciers need to reach their new equilibrium?</p><p>In this contribution, we present the experimental design of GlacierMIP3 and open up the floor for ideas and discussions about possible processing of these experiments. We also invite interested individuals and groups to join us to discuss the possibility of their model to be included in the newest phase of GlacierMIP.</p><p> </p><p><strong>References</strong></p><p><strong>GlacierMIP1</strong>: Hock, R., Bliss, A., Marzeion, B., Giesen, R.H., Hirabayashi, Y., Huss, M., Radic, V., Slangen, A.B.A. (2019), GlacierMIP – A model intercomparison of global-scale glacier mass-balance models and projections, Journal of Glaciology 65(251), 453-467, doi: 10.1017/jog.2019.22</p><p><strong>GlacierMIP2</strong>: Marzeion, B., Hock, R., Anderson, B., Bliss, A., Champollion, N., Fujita, K., Huss, M., Immerzeel, W., Kraaijenbrink, P., Malles, J-H., Maussion, F., Radic, V., Rounce, D.R., Sakai, A., Shannon, S., van de Wal, R., Zekollari, H. (2020), Partitioning the Uncertainty of Ensemble Projections of Global Glacier Mass Change, Earth’s Future 8(7), e2019EF001470, doi: 10.1029/2019EF001470</p>

scholarly journals Sea-level change in the Dutch Wadden Sea

2018 ◽  
Vol 97 (3) ◽  
pp. 79-127 ◽  
Author(s):  
Bert L.A. Vermeersen ◽  
Aimée B.A. Slangen ◽  
Theo Gerkema ◽  
Fedor Baart ◽  
Kim M. Cohen ◽  
...  
Keyword(s):  
Climate Change ◽  
Mass Loss ◽  
Sea Level Rise ◽  
Sea Level ◽  
21St Century ◽  
Wadden Sea ◽  
Recent Literature ◽  
Ghg Emissions ◽  
Sea Level Change ◽  
Level Change

AbstractRising sea levels due to climate change can have severe consequences for coastal populations and ecosystems all around the world. Understanding and projecting sea-level rise is especially important for low-lying countries such as the Netherlands. It is of specific interest for vulnerable ecological and morphodynamic regions, such as the Wadden Sea UNESCO World Heritage region.Here we provide an overview of sea-level projections for the 21st century for the Wadden Sea region and a condensed review of the scientific data, understanding and uncertainties underpinning the projections. The sea-level projections are formulated in the framework of the geological history of the Wadden Sea region and are based on the regional sea-level projections published in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5). These IPCC AR5 projections are compared against updates derived from more recent literature and evaluated for the Wadden Sea region. The projections are further put into perspective by including interannual variability based on long-term tide-gauge records from observing stations at Den Helder and Delfzijl.We consider three climate scenarios, following the Representative Concentration Pathways (RCPs), as defined in IPCC AR5: the RCP2.6 scenario assumes that greenhouse gas (GHG) emissions decline after 2020; the RCP4.5 scenario assumes that GHG emissions peak at 2040 and decline thereafter; and the RCP8.5 scenario represents a continued rise of GHG emissions throughout the 21st century. For RCP8.5, we also evaluate several scenarios from recent literature where the mass loss in Antarctica accelerates at rates exceeding those presented in IPCC AR5.For the Dutch Wadden Sea, the IPCC AR5-based projected sea-level rise is 0.07±0.06m for the RCP4.5 scenario for the period 2018–30 (uncertainties representing 5–95%), with the RCP2.6 and RCP8.5 scenarios projecting 0.01m less and more, respectively. The projected rates of sea-level change in 2030 range between 2.6mma−1for the 5th percentile of the RCP2.6 scenario to 9.1mma−1for the 95th percentile of the RCP8.5 scenario. For the period 2018–50, the differences between the scenarios increase, with projected changes of 0.16±0.12m for RCP2.6, 0.19±0.11m for RCP4.5 and 0.23±0.12m for RCP8.5. The accompanying rates of change range between 2.3 and 12.4mma−1in 2050. The differences between the scenarios amplify for the 2018–2100 period, with projected total changes of 0.41±0.25m for RCP2.6, 0.52±0.27m for RCP4.5 and 0.76±0.36m for RCP8.5. The projections for the RCP8.5 scenario are larger than the high-end projections presented in the 2008 Delta Commission Report (0.74m for 1990–2100) when the differences in time period are considered. The sea-level change rates range from 2.2 to 18.3mma−1for the year 2100.We also assess the effect of accelerated ice mass loss on the sea-level projections under the RCP8.5 scenario, as recent literature suggests that there may be a larger contribution from Antarctica than presented in IPCC AR5 (potentially exceeding 1m in 2100). Changes in episodic extreme events, such as storm surges, and periodic (tidal) contributions on (sub-)daily timescales, have not been included in these sea-level projections. However, the potential impacts of these processes on sea-level change rates have been assessed in the report.

scholarly journals Brief communication: On calculating the sea-level contribution in marine ice-sheet models

2020 ◽  
Vol 14 (3) ◽  
pp. 833-840 ◽  
Author(s):  
Heiko Goelzer ◽  
Violaine Coulon ◽  
Frank Pattyn ◽  
Bas de Boer ◽  
Roderik van de Wal
Keyword(s):  
Sea Level Rise ◽  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Ocean Water ◽  
Ice Volume ◽  
Isostatic Adjustment ◽  
The Common

Abstract. Estimating the contribution of marine ice sheets to sea-level rise is complicated by ice grounded below sea level that is replaced by ocean water when melted. The common approach is to only consider the ice volume above floatation, defined as the volume of ice to be removed from an ice column to become afloat. With isostatic adjustment of the bedrock and external sea-level forcing that is not a result of mass changes of the ice sheet under consideration, this approach breaks down, because ice volume above floatation can be modified without actual changes in the sea-level contribution. We discuss a consistent and generalised approach for estimating the sea-level contribution from marine ice sheets.

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